RDMA/vmw_pvrdma: Use refcount_dec_and_test to avoid warning

RDMA/vmw_pvrdma: Use refcount_dec_and_test to avoid warning

refcount_dec generates a warning when the operation
causes the refcount to hit zero. Avoid this by using
refcount_dec_and_test.

Fixes: 8b10ba783c9d ("RDMA/vmw_pvrdma: Add shared receive queue support")
Reviewed-by: Adit Ranadive <[email protected]>
Reviewed-by: Aditya Sarwade <[email protected]>
Reviewed-by: Jorgen Hansen <[email protected]>
Signed-off-by: Bryan Tan <[email protected]>
Reviewed-by: Leon Romanovsky <[email protected]>
Signed-off-by: Jason Gunthorpe <[email protected]>